A new U.S. Geological Survey study has discovered high levels of radon in private wells across certain areas of Pennsylvania. The study, which was conducted in cooperation with the Pennsylvania Departments of Health and Environmental Protection, examined 1,041 water wells and found that 14% had radon levels at or above the EPA proposed alternative maximum contaminant level of 4,000 picocuries per liter.

While the EPA does not currently regulate radon in drinking water, it has proposed this alternative limit for public water supplies in states like Pennsylvania, which has an EPA-approved radon indoor air quality program. For states without an approved program, the EPA has proposed a lower, more protective, maximum contaminant level of 300 picocuries per liter.

Radon, which is a colorless, odorless, radioactive gas, primarily contaminates indoor air when the gas seeps through the soil under homes and buildings, but groundwater can also be a notable indoor air radon source in areas where groundwater has extreme radon concentrations. Radon dissolved in groundwater used for drinking water can escape into the air as the water leaves a faucet, which adds to any radon that enters a structure through foundation cracks. Homeowners with private wells should be aware of the radon potential health risks because, according to the EPA, radon exposure is the second-leading cause of lung cancer in the U.S.

During the study, data collected from 1986 to 2015 from private wells were compiled to gain a better understanding of the radon levels in groundwater across the state. The USGS assessed groundwater samples from various geological formations.

For more details, see USGS report: https://pubs.er.usgs.gov/publication/sir20175018